Variable-resistance conductor terminal



Aug. 18, 1925. 1,550,2G6

F. P. CHURCH VARIABLE RESISTANCE CONDUCTOR TERMINAL Filed May 1, 1322 Im/entow Frederick P. Church, YWQ Q H is fittorn ey Patented Aug. 18, 1925.

UNlTE TATE PATENT @FFlQE.

ERlwnttICK 1. CHURCH, LYNN,MASS-ACHUSETTS, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A COBEORATION OF NEW YORK.

VARIABLE-RESISTANCE CONDUCTOR TERMINAL.

Application filed May 1,

To all whom it may concern:

Be it known that I, FREDERICK P. CHURCH, a citizen of the United States, residing at Lynn, county of Essex, State of 5 Massachusetts, have invented certain new and'ns'e'fiil Improvements in Variable-Resistance Conductor Terminals, of which the following is a specification.

My invention. relates to conductor terminals or connectors and its objectjis to provide an electric cable terminal orconnector, the impedance ofwhich may be varied in a simple manner. v

The. utility of my invention will be apparentfrom the following illustration: An electriemeter known as a shunted mercury meter has a current circuit made up of three parts, namely, the shunt, the shunt leads, and the meter. For a given meter and shunt the shunt leads must have a certain definite resistance. It is very diflicult to make up a shunt lead of a given definiteresistance due to variations in the cable of which the lead is made and variations in the usual soldered joints at its terminals. It is thus quite impomible to out a length oi cable and solder on the usual terminal clips and be sure in advance of attaining a shunt lead having a definite specific resistance. According to one form of my invention, I provide a variable resistance terminal clip or connector whichmay be soldered on to a cable in the usual way after which the resistance drop therein may be adjusted to the desired value in a manner now to be explained. 1

he features of my invention which "I believe to be novel and patentable will be pointed out in the claims appended hereto. 40 The preferred construction and use of my improved terminal clip will be understood from the following description taken in connection with the accompanying drawing in which Fig. 1 represents the details of con-. struction of a cable terminalmade in accordance with m invention and Fig. 2 illustrates the use 0 my improved terminal on meter shunt leads.

In Fig. l I'show a cable terminal clip consisting oi a, cylindrical shank l, a terminal eye 2, and a clamping nut 3. The shank portion has an axial o ening 4 in one end adapted to receive and e soldered or -.otherwise secured to an insulated cable 5. In order to secure a good conducting joint be 1922. Serial No. 557,604.

tween the cable 5 and the shank 1, their abutting surfaces may be stepped as illustrated. The other end of the shank. is provided with 'a' threaded opening 6 concentric with its axis into which a threaded extension 7 of the eye terminal 2 is adapted to be screwed. In order to secure a good electrical contact between the threaded contacting surfaces of the shank 1 and extension 7, the threaded end ofthe shank is split and is provided with an exterior conical threaded surface 8 cooperating with a clamping nut 3. The split end of the shank is caused to grip the threaded extension 7 of the eye terminal by screwing up the clamping nut 3 which is internally threaded to correspondto the threaded conical surface 8.

It will now be apparent that the length of the current path through the terminal clip maybe lengthened or shortened by screwing the eye terminal 2 out or in with respect to the shank 1 and in so doing the resistance between the extremities thereo'l will be increased ordecreased accordingly. The shank 1 and eye terminal 2. are made of metal having the required resistance to obtain the results des1redi""For shunt lead terminals 1 have found nickel steel to be very satisfactory. The nut 3 is preferably case hardened. I have. found that the re sistance of an ordinary shunt lead provided with my improved terminal clip may be varied over 10% in this manner which is more than enough to correct for any inequalities in the material of the shunt cable and variations in the resistance of the soldered joints at its end.

In Fig. 2, I havediagrammatically illustrated amercury meter 9 connected to a shunt 10 by a shunt leads 11 and 12. The meter terminals of these leads are provided with my adgiustable resistance terminal clips. Alter the shunt leads have been made up, they may be accurately adjusted to have the correct resistance drop for this particular meter and shunt by screwin the eye terminal 2 in or out of the shou 1. If at any time the meter 901' the shunt 10 is replaced and the new conditions require a difierent resistance drop in the shunt leads,it will not be necessary to provide new shunt leads because my improved terminal clip permim their resistances to be accurately adjusted to my desired value within the of the ill) device. Some users of electricity have large numbers of shunted meters and in sist on having the shunt leads interchangeable which means that the resistance of the leads should not vary above one per cent. The cut and try method of obtaining this accuracy is very expensive and is entirely unnecessary when my variable resistance terminal clip is used.

Although I have illustrated my inventionas applied to a cable terminal clip, I do not wish to be limited thereto as it will be apparent that the same idea may be applied to a cable connector. Thus, I might provide a cable connector made up of two cable receiving shanks connected together by a right and a left-hand threadedbolt. Then by turning the bolt one way, the resistance of the connector will be increased and by turning it the other way, the resistance will be decreased.

In some instances where the device is to be used on alternating current circuits it may be desirable to obtain a variable reactance instead of a variable resistance or a suitable combination of these two characteristics, in which case I will so construct my improved connector as to form an adjustable reactance. For this purpose I might make the conducting portions of the connector of material having a high skin effect such as iron and vary its length in a manner already described.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but I desire to have it understood that the apparatus shown is only illustrative, and that the invention can be carried out by other means. r

What I claim as new and desire to secure by Letters Patent of the United States, 1s,-

1. An adjustable rheostat in the form of an electric cable connector made of re sistance metal such as nickel steel, comprising a cable connecting portion and a ter minal clip portion, said parts being threaded one within the other in such a way that the length of the current path therethrough may be varied to appreciably vary the resistance.

2. An adjustable rheostat in the form of an electric terminal connector made of resistance metal .comprising a cylindrical shank having an opening in one end for receiving a cable and a threaded opening in its opposite end, said threaded end being split and provided with an exterior conical threaded surface, a terminal clip threaded into the threaded end of said shank and a clamping nut on said conical threaded exterior surface.

3. A rheostat comprising a cable connector having a longitudinal shank adapted to be secured at one end to a cable and having an internally threaded opening in its opposite end, a terminal clip provided with a threaded extension adapted to be screwed intothe threaded opening in said shank, said parts being made of a metal having a. specific resistance appreciably above that of copper and arranged so that an appre ciable variation in the resistance of the connector may be had by adjusting the position of the'said threaded clip in said shank, and means for securing said parts in any such adjusted position.

4. A meter shunt lead provided with a terminal clip designed to be used as an adjustable rheostat, said clip comprising metallic parts having a specific resistance appreciably above that of copper, said 1parts being adjustably threaded together wit the threaded ortions forming an adjustable resistance in the circuit of the shunt lead.

In witness whereof, I have hereunto set my hand this 27th day of April, 1922.

FREDERICK P. CHURCH. 

